X & the Tarot
On each X tankoubon (japanese edition only), there is an image, on the inside of the dust jacket, of a tarot card featuring one of the characters. The tarot is much more than a way to tell fortunes, it's supposed to be a sort of guide to the soul's evolution, and each card represents a different state or archtype. Consecuently, it's possible to do an analysis of the characters according to which card they correspond to.
Click on each card to read its analysis. I'm sorry that there's so few actually done, but writting this takes awhile.